First one is the 69 scene. If Shuu is a dom top, he'll initiate the position. You have to make Haato give Shuu a BJ (one that results three of the top row of chibis, I believe) every sexual encounter they have. For my playthrough, it took three sexual encounters before the scene triggered. The second one is simply Shuu bottoming for Haato--an alternate take during their first time together. From what I remember, you can trigger that scene if you choose to have Haato top Shuu.